Counterweight and method for recycling the same

ABSTRACT

The present invention provides a counterweight and a counterweight-recycling method capable of having excellent workability, capable of reducing manufacturing costs, and capable of achieving environmental conservation. A metal portion contained in slag produced in an iron making process or in residue in a waste treatment furnace is used as a weight material of a counterweights. A method of recycling the counterweight includes a removing step of removing an outer shell of a used counterweight that has used a magnetic metal portion as a weight material, a crushing/cutting step of crushing a filler containing the metal portion of the counterweight from which the outer shell has been removed and destroying a combined state between the metal portion and the other filler portion, and a separating step of separating processed products obtained in the crushing/cutting step into high-specific-gravity substances composed chiefly of the metal portion and into other low-specific-gravity substances, in which the high-specific-gravity substances are used as weight materials of a counterweight to be newly manufactured.

TECHNICAL FIELD

The present invention relates to a counterweight mounted on aconstruction machine, such as a hydraulic shovel, and to a recyclingmethod of the counterweight.

BACKGROUND ART

Generally, a construction machine, such as a hydraulic shovel, isprovided with a counterweight used to maintain the balance of a machinebody, for example, while the machine is operating. The counterweight isproduced, for example, by filling the interior of a hollow outer shellmade of sheet steel with a filler in which metal pieces (e.g., iron oreor iron pieces) used as weight materials are held together with cementor other materials.

Conventionally, the counterweight has been subjected to waste disposalafter having been used, but, in recent years, an attempt to recycle thecounterweight has been made in accordance with the promotion ofrecycling in many fields. In this case, a proposal has been made torecover the metal portion great in specific gravity from the usedcounterweight and then mix and use the metal portion with a filler of anew counterweight.

However, the counterweight and the recycling method have the followingproblems.

When a metal portion is recovered from a used counterweight by crushingand separating a filler into the metal portion and into the other fillerportion, cement has easily been included in the metal portion.Therefore, cases have occurred in which the bulk specific gravity ofrecovered substances does not reach a given value, or the recoveredsubstances do not have bulk specific gravity usable as weight materials.Therefore, when such recovered substances are used to manufacture newcounterweights, an operation to adjust the weight of each counterweightis needed, and, disadvantageously, much time is consumed because of lowworkability, thus raising manufacturing costs.

Additionally, when a brittle material like pig iron is used as a metalportion, the metal portion also is easily crushed in crushing a filler,and therefore the range of particle size distribution of the metalportion that has been recovered has had a tendency to be narrower thanthe range of the metal portion obtained when a counterweight ismanufactured. Hence, the bulk specific gravity of recovered substancesbecomes small, and cases have occurred in which the recovered substancesdo not have bulk specific gravity usable as weight materials. Therefore,disadvantageously, much time is consumed because of low workability whennew counterweights are manufactured, thus raising manufacturing costs.

Additionally, materials having low adsorptivity to a magnet are oftencontained in the metal portion, and therefore, when the metal portion isextracted from a used counterweight, a conventional drum-type magneticseparator of low peripheral speed/low magnetic force had the possibilitythat the recovered substances could not be easily separated from eachother.

The present invention has been made in consideration of the foregoingcircumstances. It is therefore an object of the present invention toprovide a counterweight and a recycling method thereof capable of havingexcellent workability, capable of reducing manufacturing costs, andcapable of achieving environmental conservation.

SUMMARY OF THE INVENTION

A counterweight according to a first aspect of the present inventionwith the aforementioned object uses a metal portion contained in slagproduced during an iron making process or contained in residue left in awaste treatment furnace as a weight material. Accordingly, since themetal portion contained in the slag or residue, which has conventionallybeen subjected to waste disposal, can be used as a weight material, themetal portion can be effectively used.

A counterweight according to a second aspect of the present invention ischaracterized in that a metal portion obtained by crushing a usedcounterweight in which slag produced during an iron making process or ametal portion contained in residue left in a waste treatment furnace isused as a weight material is used as a new weight material. Accordingly,the metal portion contained in the slag or in the residue, which hasconventionally been subjected to waste disposal, can be effectivelyused, and the metal portion can be recycled.

A method of recycling a counterweight according to the present inventionhas a removing step of removing an outer shell of a used counterweightthat has used a magnetic metal portion as a weight material, acrushing/cutting step of crushing a filler containing the metal portionof the counterweight from which the outer shell has been removed andcutting a combined state between the metal portion and the other fillerportion, and a separating step of separating processed products obtainedin the crushing/cutting step into high-specific-gravity substancescomposed chiefly of the metal portion and into otherlow-specific-gravity substances, in which the high-specific-gravitysubstances are used as a weight material of a counterweight to be newlymanufactured. Accordingly, since the method has the removing step, thecrushing/cutting step, and the separating step, bulk specific gravityusable as a weight material can be provided, and high-specific-gravitysubstances composed chiefly of a metal portion having substantiallyfixed bulk specific gravity can be easily recovered.

Preferably, in the method of recycling the counterweight according tothe present invention, the metal portion is a mass of metal recoveredfrom slag produced in at least one of a blast furnace, a cupola furnace,a converter, and an electric furnace, or is a mass of metal contained inresidue in a waste treatment furnace. Accordingly, since the metalportion contained in the slag or in the residue that has conventionallybeen subjected to, for example, waste disposal can be used as a weightmaterial, the metal portion can be effectively used.

Preferably, in the method of recycling the counterweight according tothe present invention, large-sized metal pieces are removed by roughlycrushing the filler containing the metal portion, and thereafter theremaining filler portion is further crushed so as to cut a combinedstate between the metal portion and the other filler portion in thecrushing/cutting step. Thus, since the filler is first of all roughlycrushed, the large-sized metal pieces that have difficulty in beingrecycled as weight materials can be easily removed from the filler.Since the filler from which the large-sized metal pieces have beenremoved is further crushed after that, the filler can be easily crushedwithout any influence of the large-sized metal pieces.

Preferably, in the method of recycling the counterweight according tothe present invention, the processed products are separated intohigh-specific-gravity substances composed substantially of metal piecesand into low-specific-gravity substances by a magnetic separator of highperipheral speed/high magnetic force in the separating step. Thus, sincethe processed products are put into the magnetic separator of highperipheral speed/high magnetic force so as to recover thehigh-specific-gravity substances composed substantially of metal pieces,the ratio of low-specific-gravity substances involved in thehigh-specific-gravity substances can be reduced.

Preferably, in the method of recycling the counterweight according tothe present invention, the processed products are magnetically separatedby a conventional magnetic separator, and the processed productsseparated onto a magnetic-substance side (i.e., side of magneticallyattracted substances) are further separated by the magnetic separator ofhigh peripheral speed/high magnetic force into high-specific-gravitysubstances composed substantially of metal pieces and intolow-specific-gravity substances in the separating step. Thus, since theprocessed products are first of all magnetically separated so as torecover the processed products separated onto the magnetic-substanceside, separable non-magnetic substances can be easily removed from theprocessed products. Since the processed products are further put intothe magnetic separator of high peripheral speed/high magnetic force soas to recover the high-specific-gravity substances composedsubstantially of metal pieces after that, the ratio oflow-specific-gravity substances involved in the high-specific-gravitysubstances can be reduced.

Preferably, in the method of recycling the counterweight according tothe present invention, the peripheral speed of the magnetic separator ofhigh peripheral speed/high magnetic force is 300 to 500 m/min. Thereby,since the high-specific-gravity substances are magnetically attracted tothe magnetic separator, and since the low-specific-gravity substancesare blown off from the magnetic separator, separation accuracy betweenthe high-specific-gravity substances and the low-specific-gravitysubstances can be improved.

Preferably, in the method of recycling the counterweight according tothe present invention, the magnetic flux density of the magneticseparator of high peripheral speed/high magnetic force is more than4,000 gausses. Thereby, since the ratio of the high-specific-gravitysubstances magnetically attracted to the magnetic separator increases,separation accuracy between the high-specific-gravity substances and thelow-specific-gravity substances can be improved.

Preferably, in the method of recycling the counterweight according tothe present invention, the processed products are separated by anair-blast separator into high-specific-gravity substances composedsubstantially of metal pieces and into low-specific-gravity substancesin the separating step. Thus, since the high-specific-gravity substancescomposed substantially of metal pieces are recovered by putting theprocessed products into the air-blast separator, the ratio of thelow-specific-gravity substances involved in the high-specific-gravitysubstances can be reduced.

Preferably, in the method of recycling the counterweight according tothe present invention, the processed products are magnetically separatedby a conventional magnetic separator, and the processed productsseparated to the magnetic-substance side are further separated by theair-blast separator into high-specific-gravity substances composedsubstantially of metal pieces and into low-specific-gravity substancesin the separating step. Thus, since the processed products are first ofall magnetically separated so as to recover the processed productsseparated to the magnetic-substance side, separable non-magneticsubstances can be easily removed from the processed products. Sincethese processed products are further put into the air-blast separator soas to recover high-specific-gravity substances composed substantially ofmetal pieces after that, the ratio of the low-specific-gravitysubstances involved in the high-specific-gravity substances can bereduced.

Preferably, in the method of recycling the counterweight according tothe present invention, the wind power of the air-blast separator is 12to 20 m/s. Thereby, since the ratio of the low-specific-gravitysubstances blown off by the wind power of the air-blast separatorincreases, separation accuracy between the high-specific-gravitysubstances and the low-specific-gravity substances can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a hydraulic shovel that has a counterweightaccording to one embodiment of the present invention.

FIG. 2 is a perspective view of the counterweight.

FIG. 3 is an explanatory drawing explaining a method of recycling acounterweight according to one embodiment of the present invention.

FIG. 4 is a front sectional view of a dry magnetic separator that isapplicable to the counterweight-recycling method.

FIG. 5 is an explanatory drawing of examination results according to theembodiment.

PREFERRED EMBODIMENT OF THE INVENTION

An embodiment that embodies the present invention will be described withreference to the attached drawings, thereby ensuring a betterunderstanding of the present invention.

FIG. 1 is a side view of a hydraulic shovel that has a counterweightaccording to one embodiment of the present invention, FIG. 2 is aperspective view of the counterweight, FIG. 3 is an explanatory drawingexplaining a method of recycling a counterweight according to oneembodiment of the present invention, FIG. 4 is a front sectional view ofa dry magnetic separator that is applicable to thecounterweight-recycling method, and FIG. 5 is an explanatory drawing ofexamination results according to the embodiment.

As shown in FIG. 1 and FIG. 2, the counterweight 10 according to oneembodiment of the present invention is mounted on the rear end portionof the hydraulic shovel 11 that is one example of a constructionmachine, and is used to maintain the machine balance of the hydraulicshovel 11 while the hydraulic shovel 11 is operating, for example. Adetailed description thereof will be given hereinafter.

The hydraulic shovel 11 comprises a crawler-type lower structure 12, anupper structure 13 rotatably supported on the lower structure 12, and afront attachment 14 attached to the front part of the upper structure13, and, in order to maintain a gravity balance with the frontattachment 14 or a load (not shown), the counterweight 10 is mounted onthe hydraulic shovel 11.

The counterweight 10 is structured by filling the interior of a hollowouter shell 15 made of sheet steel that forms the outer part of thecounterweight 10 with a filler. The filler is manufactured by holdingtogether a metal portion used as a weight material and iron pieces thatare one example of large-sized metal portion for weight adjustment withcement that is one example of other fillers. Concrete can be used asother fillers.

The metal portion is a mass of metal recovered from manufacture-ironslag (one example of slag) produced when iron ore, cast iron, etc., aremelted in an iron making process in a blast furnace or a cupola furnace,or is a mass of metal contained in residue produced when waste (garbage)is gasified in a waste treatment furnace. It is also possible to use, asa weight material in manufacturing a new counterweight, a metal portionobtained by crushing a used counterweight in which the metal portion,which is contained in the slag produced in the iron making process orwhich is contained in the residue in the waste treatment furnace, hasbeen used as a weight material.

Because either metal portion left in the furnace can be easily obtainedat a low price, the manufacturing costs of the counterweight 10 can beeconomically reduced.

The hydraulic shovel 11 is aging by being used for a long time. Whensuch a aging hydraulic shovel is processed, the counterweight 10 isrecycled according to the following method.

As shown in FIG. 3, a method of recycling a counterweight according toone embodiment of the present invention has a removing step of removingan outer shell 15 of a used counterweight 10 that has used a magneticmetal portion as a weight material, a crushing/cutting step of crushinga filler containing the metal portion of the counterweight 10 from whichthe outer shell 15 has been removed and cutting a combined state betweenthe metal portion and the cement, and a separating step of separatingprocessed products obtained in the crushing/cutting step intohigh-specific-gravity substances composed chiefly of the metal portionand into other low-specific-gravity substances (for example,non-magnetic substances and low-specific-gravity substances), in whichthe high-specific-gravity substances are used as weight materials of acounterweight to be newly manufactured. A detailed description thereofwill be given hereinafter.

First of all, in step 1 (ST1), the counterweight 10 is detached from theaging hydraulic shovel 11, and the outer shell 15 made of sheet steel isremoved from the counterweight 10. Namely, the outer shell 15 isseparated from the counterweight 10 with a crusher or the like, and,especially in a large-sized counterweight, the removing operation can beefficiently performed by separating the outer shell after partiallycutting the outer shell with a gas cutting machine (melting machine) ora cutter. The removed outer shell 15 can be recovered as an iron scrapand can be recycled (the foregoing description concerns the removingstep).

In step 2 (ST2), the filler from which the outer shell 15 has beenremoved is roughly crushed into pieces each of which being about thesize of a fist (5 to 15 cm in diameter), for example, with a crusher(breaker) or the like, and separable iron pieces are removed. Steelmaterials are included as a large-sized metal portion to be roughlycrushed and separated, and removed iron pieces and steel materials arerecovered as iron scrap and are recycled.

In step 3 (ST3), the remaining filler obtained by extracting ironpieces, steel materials, etc., from the roughly crushed filler is groundwith a rod mill or a ball mill serving as a grinder so that the particlediameter is, for example, 7 mm or less, whereby a combined state betweenthe metal portion and the cement is cut, namely dissolved. Crush andground of the metal portion is controlled to minimum, and the cementthat performs its role as a binder of each particle that constitutes themetal portion is chiefly crushed and ground. Thus, a combined statebetween the metal portion and the cement can be cut (dissolved) byappropriately controlling the crushing and grinding of the metal portion(the foregoing description concerns the crushing/cutting step).

In step 4 (ST4), the processed products that have been ground aremagnetically separated by a conventional magnetic separator intomagnetic substances and non-magnetic substances (one example of otherlow-specific-gravity substances). The magnetic separator used herein isa well-known drum-type magnetic separator of low peripheral speed/lowmagnetic force (i.e., DPT magnetic separator), and the peripheral speedof the drum can be set at about 120 m/min, and the magnetic flux densitycan be set at about 1,500 gausses (0.15 Tesla), for example. It ispreferable to further sift and select the magnetic substances and toremove, as iron scrap, particles larger in particle diameter (forexample, about 2 cm or more), i.e., particles that cannot be used as themetal portion. Thereby, it becomes possible to approximate the bulkspecific gravity of the metal portion to a more uniform value. Sincenon-magnetic substances are included in the magnetic substances, theprocessed products that have been separated onto a magnetic-substanceside, i.e., the magnetic substances including the non-magneticsubstances are further separated by the magnetic separator(separator) ofhigh peripheral speed/high magnetic force into high-specific-gravitysubstances composed substantially of metal pieces and intolow-specific-gravity substances (one example of otherlow-specific-gravity substances) in step 5 (ST5). The magnetic separatorof high peripheral speed/high magnetic flux is a conventionally knownmagnetic separator, in which a plurality of magnets arranged so that thepolarities of adjoining magnets differ from each other are arcuatelyfixed inside a cylindrical drum that is rotated and driven by arotating/driving source, whereby materials that fall onto thecylindrical drum are separated into magnetic high-specific-gravitysubstances and into non-magnetic low-specific-gravity substances.

As shown in FIG. 4, a dry magnetic separator 20 disclosed, for example,in Japanese Patent Application No. H10-309415 can be used as themagnetic separator of high peripheral speed/high magnetic flux. The drymagnetic separator 20 is rotatably provided in a casing 21, and includesa cylindrical drum 24 that allows materials consisting of magneticsubstances 22 and non-magnetic substances 23 thrown from above to fallalong the front surface, a magnetic-field generating mechanism 27 thatis fixed and disposed to a magnet mounting plate 26 so that magnets 25adjoining in the circumferential direction inside the cylindrical drum24 have polarities different from each other and by which a magneticfield is generated on the surface of the cylindrical drum 24, and amagnetic-substance recovering part 28 and a non-magnetic-substancerecovering part 29 that are disposed under the cylindrical drum 24 andrecover the magnetic substances 22 and the non-magnetic substances 23,respectively, separated magnetically. A hopper 30 used to cast rawmaterials to the upper part of the cylindrical drum 24 is provided abovethe cylindrical drum 24. A feeder 31 used to feed the raw materials tothe hopper 30 is provided above the hopper 30.

In the dry magnetic separator 20, the magnetic substances 22 among theraw materials, which have undergone an adjustment of the amount to becast through a damper 32 and which have been cast onto the cylindricaldrum 24 rotating at high speed, are attracted by a magnetic fieldgenerated by the magnetic-field generating mechanism 27 onto the surfaceof the cylindrical drum 24, and the non-magnetic substances 23 amongthem reach the state of lying on the surface of the cylindrical drum 24.Thereafter, the magnetic substances 22 withdraw from the magnetic forceof the magnetic-field generating mechanism 27 while performinginversion, are then separated from the surface of the cylindrical drum24, and are recovered into the magnetic-substance recovering part 28. Incontrast, the non-magnetic substances 23 are quickly separated from thesurface of the cylindrical drum 24 because of release from the magneticsubstances 22 and because of influence of a strong centrifugal forcewhen the magnetic substances 22 perform inversion, and are recoveredinto the non-magnetic-substance recovering part 29. Themagnetic-substance recovering part 28 and the non-magnetic-substancerecovering part 29 are divided by a partition plate 33.

In the magnetic separator of high peripheral speed/high magnetic force,the peripheral speed of the cylindrical drum is set to be 300 to 500m/min, and the magnetic flux density is set to be more than 4,000gausses (0.4 Tesla) in consideration of the state of substances to beseparated, i.e., in consideration of whether or not they are easilyattracted to the cylindrical drum, or in consideration of their shapes.

If the peripheral speed of the cylindrical drum is less than 300 m/min,the low-specific-gravity substances included in thehigh-specific-gravity substances cannot be blown off, and thehigh-specific-gravity substances cannot be sufficiently separated fromthe low-specific-gravity substances. Therefore, there is the possibilitythat the bulk specific gravity of recovered high-specific-gravitysubstances cannot reach a targeted value. On the other hand, if theperipheral speed of the cylindrical drum exceeds 500 m/min, theperipheral speed of the cylindrical drum increases, and the amount ofthe high-specific-gravity substances attracted onto the cylindrical drumdecreases, and, uneconomically, the yield of the high-specific-gravitysubstances decreases. Therefore, in order to improve separation accuracybetween the high-specific-gravity substances and thelow-specific-gravity substances and raise the yield of thehigh-specific-gravity substances, it is desirable to set the peripheralspeed of the cylindrical drum at 350 to 500 m/min, and more desirably,400 to 480 m/min.

If the magnetic flux density of the cylindrical drum is less than 4,000gausses, the peripheral speed of the cylindrical drum increases, and theamount of the high-specific-gravity substances attracted onto thecylindrical drum decreases, and, uneconomically, the yield of thehigh-specific-gravity substances decreases. On the other hand, if themagnetic flux density is high, a fall in the amount of thehigh-specific-gravity substances attracted onto the cylindrical drum canbe controlled in spite of the fact that the peripheral speed of thecylindrical drum increases, and therefore a specified upper limit valueis not predetermined. However, it is desirable to set the upper limitvalue at 10,000 gausses, in consideration of the running cost of themagnetic separator of high peripheral speed/high magnetic force or inconsideration of the performance of the device.

A conventionally known air-blast separator can be used instead of themagnetic separator of high peripheral speed/high magnetic force. Thewind power of the air-blast separator is set at 12 to 20 m/s inaccordance with the state of substances to be separated, i.e., theirspecific gravities or shapes.

If the wind power is less than 12 m/s, the low-specific-gravitysubstances included in the high-specific-gravity substances cannot beblown off, and the high-specific-gravity substances cannot besufficiently separated from the low-specific-gravity substances.Therefore, there is the possibility that the bulk specific gravity ofrecovered high-specific-gravity substances cannot reach a targetedvalue.

On the other hand, if the wind power exceeds 20 m/s, thehigh-specific-gravity substances will be blown off together with thelow-specific-gravity substances with a high probability, and therefore,not only can a sufficient separation between the high-specific-gravitysubstances and the low-specific-gravity substances not be made, but therecovering rate of the high-specific-gravity substances will decrease.Therefore, in order to improve separation accuracy between thehigh-specific-gravity substances and the low-specific-gravity substancesand raise the yield of the high-specific-gravity substances, it isdesirable to set the wind power at 12.5 to 17 m/s, and more desirably,13 to 15 m/s.

Accordingly, the magnetic substances recovered by the DPT magneticseparator can be easily separated into high-specific-gravity substancescomposed chiefly substantially of metal pieces and into the otherlow-specific-gravity substances (the foregoing description concerns theseparating step).

The high-specific-gravity substances recovered according to theaforementioned method are mixed with a filler of a counterweight to benewly manufactured. Tests reveal the fact that 80% or more of a usedcounterweight can be recycled by mixing the high-specific-gravitysubstances with pieces recovered as iron scrap. Therefore, themanufacturing cost of the counterweight to be newly manufactured can bereduced, and environmental conservation can be achieved.

A description will be given of results for which thecounterweight-recycling method according to the present invention hasbeen applied, and examinations have been made.

Preferably, a bulk specific gravity of 2.9 or more can be achieved as atargeted value in order to use a recovered metal portion as a weightmaterial of a counterweight.

Herein, the bulk specific gravities and the yields of the recoveredhigh-specific-gravity substances are calculated and compared by use ofthe DPT magnetic separator, the conventionally known air-blastseparator, and the magnetic separator of high peripheral speed/highmagnetic force when processed products (before separation: bulk specificgravity 2.53) that have been recovered with the DPT magnetic separatorand have been separated onto the magnetic-substance side are separatedinto high-specific-gravity substances composed chiefly of the metalportion and into the other low-specific-gravity substances (for example,cement). Examination results obtained by use of the DPT magneticseparator, the air-blast separator, and the magnetic separator of highperipheral speed/high magnetic force are shown in Tables 1 through 3,respectively, and in FIG. 5. TABLE 1 Before After separation Caseseparation 1 2 Peripheral speed (m/min) — 120 200 Yield ofhigh-specific-gravity 100 96 83 substances (%) Bulk specific gravity2.53 2.54 2.60

TABLE 2 Before After separation Case separation 3 4 5 Wind speed (m/s) —7.8 10.3 13.9 Yield of high-specific-gravity 100 97 88 74 substances (%)Bulk specific gravity 2.53 2.59 2.73 2.93

TABLE 3 Before After separation Case separation 6 7 8 9 Peripheral speed— 270 340 410 430 (m/min) Yield of high- 100 91 88 85 84specific-gravity substances (%) Bulk specific gravity 2.53 2.70 2.782.91 2.97

As in Case 1, the DPT magnetic separator is normally used under thecondition that the peripheral speed of the drum is set at about 120m/min, and the magnetic flux density is 1,500 gausses (0.15 Tesla), and,in this case, the bulk specific gravity is 2.54. From this, it isunderstood that the bulk specific gravity after separation almost neverincreases in comparison with the bulk specific gravity beforeseparation. Additionally, as in Case 2, the bulk specific gravity wasraised to 2.60 by increasing the peripheral speed of the drum up to 200m/min, but 2.9, which is the targeted value, could not be obtained.

As in Case 4, in the air-blast separator, the bulk specific gravityreached 2.73 by increasing the wind power up to 10.3 m/s, and a valuegreater than that of the DPT magnetic separator was obtained, but 2.9,which is the targeted value, could not be obtained. However, the bulkspecific gravity reached 2.93 by increasing the wind power up to 13.9m/s. The obtained value is over the targeted value 2.9. At this time,the yield of the high-specific-gravity substances is 74 weight percent.

Using the magnetic separator of high peripheral speed/high magneticforce, examinations were made while fixing the magnetic flux density at4,000 gausses (0.40 Tesla). As in Case 8, the bulk specific gravityreached 2.91 by increasing the peripheral speed of the cylindrical drumup to 410 m/min. The targeted value 2.9 was achieved. At this time, theyield of the high-specific-gravity substances was 85 weight percent.From this, it is understood that the yield was greatly raised incomparison with 74 weight percent of the air-blast separator.

Additionally, as in Case 9, the bulk specific gravity could be furtherraised to be 2.97 by increasing the peripheral speed of the cylindricaldrum up to 430 m/min. At this time, the yield of thehigh-specific-gravity substances was reduced only by about 1% incomparison with that of Case 8. From this, it is understood that a highyield was maintained. In other words, the bulk specific gravity and theyield of the high-specific-gravity substances can be raised by using themagnetic separator of high peripheral speed/high magnetic force.

From these results, it is understood that separation accuracy betweenthe high-specific-gravity substances and the low-specific-gravitysubstances was improved by using the magnetic separator of highperipheral speed/high magnetic force, and the high-specific-gravitysubstances that were controlled not to mix with cement, which is thelow-specific-gravity substance, could be recovered.

Therefore, the recovered high-specific-gravity substances can be mixedwith a filler of a counterweight to be newly manufactured, and,economically, material costs can be reduced.

The present invention has been described in connection with theembodiment as mentioned above. However, without being limited to thestructures mentioned in the embodiment, the present invention includesother embodiments and modifications without departing from the scope ofthe invention as defined in the appended claims.

For example, the present invention is applicable to a case in which thecounterweight and the recycling method of the present invention arestructured by combining parts or all of the other embodiments andmodifications together.

In the aforementioned embodiment, a case has been described in which themetal portion is a mass of metal recovered from manufacture-iron slagproduced when iron ore, cast iron, etc., are melted in an iron makingprocess in a blast furnace or a cupola furnace. However, for example, asanother metal portion, use can be made of metal pieces recovered fromslag produced in a converter and an electric furnace, or in at least twoof either the blast furnace, the cupola furnace, the converter, and theelectric furnace.

Additionally, in the aforementioned embodiment, a case has beendescribed in which the processed products are magnetically separated bythe DPT magnetic separator, and the processed products separated onto amagnetic-substance side are further separated by the magnetic separatorof high peripheral speed/high magnetic force into high-specific-gravitysubstances and into low-specific-gravity substances in the separatingstep.

However, only one magnetic separator of high peripheral speed/highmagnetic force or only one air-blast separator can be used, or,alternatively, a plurality of magnetic separators of high peripheralspeed/high magnetic force or a plurality of air-blast separators can beused in accordance with the amount of impurities to be mixed with thefiller or the state (for example, specific gravity or shape) of themetal portion, without using the conventional magnetic separator. If theplurality of magnetic separators of high peripheral speed/high magneticforce are used, low-specific-gravity substances involved inhigh-specific-gravity substances are gradually removed by graduallyincreasing the peripheral speed of each magnetic separator downstreamand gradually increasing the magnetic flux density downstream. If theplurality of air-blast separators are used, low-specific-gravitysubstances involved in high-specific-gravity substances are graduallyremoved by gradually increasing the wind power of each air-blastseparator downstream. As a result, the bulk specific gravity or therecovering rate of the high-specific-gravity substances can be furtherraised.

Additionally, in the aforementioned embodiment, a case has beendescribed in which the processed products are magnetically separated bythe DPT magnetic separator, and then the processed products are furtherseparated by the magnetic separator of high peripheral speed/highmagnetic force or by the air-blast separator into high-specific-gravitysubstances and into low-specific-gravity substances in the separatingstep. However, the processed products can also be separated intohigh-specific-gravity substances and into low-specific-gravitysubstances by use of a wet jig instead of the magnetic separator of highperipheral speed/high magnetic force or the air-blast separator.

In a counterweight as set forth in Claim 1, since a metal portioncontained in slag or in residue that has conventionally been subjectedto waste disposal can be used as a weight material, the metal portioncan be effectively used. Therefore, economically, costs needed tomanufacture the counterweight and costs needed for waste disposal can bereduced.

In a counterweight as set forth in Claim 2, a metal portion contained inslag or in residue, which has conventionally been subjected to wastedisposal, can be effectively used, and the metal portion can berecycled. Therefore, costs needed to manufacture the counterweight andcosts needed for waste disposal can be reduced, and environmentalconservation can be ensured by reducing waste.

In a method of recycling a counterweight as set forth in any one ofClaims 3 through 12, since a removing step, a crushing/cutting step, anda separating step are included, bulk specific gravity usable as a weightmaterial can be provided, and high-specific-gravity substances composedchiefly of a metal portion including substantially fixed bulk specificgravity can be easily recovered. Therefore, since an operation to adjustthe weight of each counterweight is not needed when new counterweightsare manufactured, excellent workability can be obtained, andmanufacturing costs can be reduced. Additionally, since a metal portioncontained in a filler of a used counterweight can be recycled, acounterweight-recycling method can be provided by which environmentalconservation can be ensured by reducing waste.

In a method of recycling a counterweight as set forth in Claim 4, sincea metal portion contained in slag or in residue that has conventionallybeen subjected to waste disposal can be used as a weight material, themetal portion can be effectively used. Therefore, economically, costsneeded for waste disposal can be reduced.

In a method of recycling a counterweight as set forth in Claim 5, sincea filler is first of all roughly crushed, large-sized metal pieces thathave difficulty in being recycled as weight materials can be easilyremoved from the filler. Since the filler from which the large-sizedmetal pieces have been removed is further crushed after that, the fillercan be easily crushed without any influence of the large-sized metalpieces. Therefore, since separation accuracy between the metal portionand the other filler portion can be improved, the bulk specific gravityof high-specific-gravity substances can be raised, and the quality ofcounterweights to be manufactured can be improved.

Additionally, since the filler is gradually crushed when a brittlematerial like pig iron is used as a metal portion, the metal portion canbe prevented from being roughly crushed when the filler is crushed.Therefore, since the range of a particle-size distribution of the metalportion that has been crushed can be made almost the same as that of themetal portion obtained when the counterweight is manufactured, recoveredsubstances can have bulk specific gravity usable as a weight material.Therefore, since recovered metal pieces can be used without beingsubjected to any treatment when a new counterweight is manufactured,excellent workability can be achieved, and manufacturing costs can bereduced.

Additionally, since the filler that has been roughly crushed and fromwhich large-sized metal pieces have been removed is further crushed, andsince a crusher is not damaged by the metal pieces, economies areachieved.

In a method of recycling a counterweight as set forth in Claim 6, sincehigh-specific-gravity substances composed substantially of metal piecesare recovered by a magnetic separator of high peripheral speed/highmagnetic force, the ratio of low-specific-gravity substances included inthe high-specific-gravity substances can be reduced. Therefore, sincethe high-specific-gravity substances can be efficiently recovered fromprocessed products, excellent workability can be achieved.

In a method of recycling a counterweight as set forth in Claim 7, sinceprocessed products are first of all magnetically separated so as torecover the processed products separated onto the magnetic-substanceside, separable non-magnetic substances can be easily removed from theprocessed products. Since the processed products are further put intothe magnetic separator of high peripheral speed/high magnetic force soas to recover the high-specific-gravity substances composedsubstantially of metal pieces after that, the ratio oflow-specific-gravity substances involved in the high-specific-gravitysubstances can be reduced. Therefore, since the processed products aregradually separated, the high-specific-gravity substances can beefficiently recovered, and workability is excellent.

Additionally, since the metal pieces are attracted and recovered to themagnetic separator of high peripheral speed/high magnetic force whenhigh-specific-gravity substances are extracted from a usedcounterweight, they are easily separated, and high-specific-gravitysubstances can be efficiently recovered even when materials having lowadsorptivity to a magnet are contained as the metal pieces.

In a method of recycling a counterweight as set forth in Claim 8, sincehigh-specific-gravity substances are magnetically attracted to themagnetic separator, and since low-specific-gravity substances are blownoff from the magnetic separator, separation accuracy between thehigh-specific-gravity substances and the low-specific-gravity substancescan be improved. Therefore, since the quality of thehigh-specific-gravity substances can be improved, the recoveredhigh-specific-gravity substances can be easily used to manufacture a newcounterweight, and the quality of a counterweight to be manufactured canbe improved.

In a method of recycling a counterweight as set forth in Claim 9, sincethe ratio of high-specific-gravity substances magnetically attracted tothe magnetic separator is raised, separation accuracy between thehigh-specific-gravity substances and the low-specific-gravity substancescan be improved. Therefore, since the quality of thehigh-specific-gravity substances can be improved, the recoveredhigh-specific-gravity substances can be easily used to manufacture a newcounterweight, and the quality of a counterweight to be manufactured canbe improved.

In a method of recycling a counterweight as set forth in Claim 10, sinceprocessed products are put into an air-blast separator so as to recoverhigh-specific-gravity substances composed substantially of metal pieces,the ratio of low-specific-gravity substances involved in thehigh-specific-gravity substances can be reduced. Therefore, since thehigh-specific-gravity substances can be efficiently recovered from theprocessed products, workability is excellent.

In a method of recycling a counterweight as set forth in Claim 11, sinceprocessed products are first of all magnetically separated so as torecover the processed products separated onto the magnetic-substanceside, separable non-magnetic substances can be easily removed from theprocessed products. Since the processed products are further put intothe air-blast separator so as to recover the high-specific-gravitysubstances composed substantially of metal pieces after that, the ratioof low-specific-gravity substances involved in the high-specific-gravitysubstances can be reduced. Therefore, since the processed products aregradually separated, the high-specific-gravity substances can beefficiently recovered, and workability is excellent.

Additionally, since the high-specific-gravity substances are separatedand recovered by the air-blast separator when the high-specific-gravitysubstances are extracted from a used counterweight, thehigh-specific-gravity substances are easily separated and can beefficiently recovered even when materials having low adsorptivity to amagnet are contained as the metal pieces.

In a method of recycling a counterweight as set forth in Claim 12, sincethe ratio of low-specific-gravity substances blown off by wind power ofthe air-blast separator is raised, separation accuracy between thehigh-specific-gravity substances and low-specific-gravity substances canbe improved. Therefore, since the quality of the high-specific-gravitysubstances can be improved, the recovered high-specific-gravitysubstances can be easily used to manufacture a new counterweight, andthe quality of a counterweight to be manufactured can be improved.

Industrial Applicability

The present invention can be widely applied to a case where acounterweight mounted on a construction machine, such as a hydraulicshovel, is manufactured and to a case where such a counterweight isrecycled. Workability can be improved, manufacturing costs can bereduced, and environmental conservation can be achieved by carrying outthe present invention.

1. A counterweights wherein a metal portion contained in slag producedin an iron making process or in residue in a waste treatment furnace isused as a weight material.
 2. A counterweight, wherein a metal portionis used as new weight materials, the metal portion having been obtainedby crushing a used counterweight in which the metal portion contained inslag produced in an iron making process or in residue in a wastetreatment furnace was used as weight materials.
 3. A method of recyclinga counterweight, the method comprises: a removing step of removing anouter shell of a used counterweight that has used a magnetic metalportion as a weight material; a crushing/cutting step of crushing afiller containing the metal portion of the counterweight from which theouter shell has been removed and destroying a combined state between themetal portion and the other filler; and a separating step of separatingprocessed products obtained in the crushing/cutting step intohigh-specific-gravity substances composed chiefly of the metal portionand into the other low-specific-gravity substances, wherein thehigh-specific-gravity substances are used as weight materials of newlymanufactured counterweights.
 4. The method of recycling a counterweightas set forth in claim 3, wherein the metal portion includes metal thatis recovered from slag produced from at least one of a blast furnace, acupola furnace, a converter, and an electric furnace, or is metalcontained in residue in a waste treatment furnace.
 5. The method ofrecycling a counterweight as set forth in claim 3, wherein, in thecrushing/cutting step, a filler containing the metal portion is roughlycrushed to remove a large-sized metal portion, and thereafter theremaining filler is further crushed to destroy a combined state betweenthe metal portion contained in the remaining filler and the otherfiller.
 6. The method of recycling a counterweight as set forth in claim3, wherein, in the separating step, the processed products are separatedby a magnetic separator of high peripheral speed/high magnetic forceinto the high-specific-gravity substances composed substantially of ametal portion and into low-specific-gravity substances.
 7. The method ofrecycling a counterweight as set forth in claim 3, wherein, in theseparating step, the processed products are magnetically separated by aconventional magnetic separator, and the processed products separatedonto a magnetic-substance side are further separated by a magneticseparator of high peripheral speed/high magnetic force into thehigh-specific-gravity substances composed substantially of a metalportion and into the low-specific-gravity substances.
 8. The method ofrecycling a counterweight as set forth in claim 6, wherein a peripheralspeed of the magnetic separator of high peripheral speed/high magneticforce is 300 to 500 m/min.
 9. The method of recycling a counterweight asset forth in claim 6, wherein a magnetic flux density of the magneticseparator of high peripheral speed/high magnetic force is more than 4000gausses.
 10. The method of recycling a counterweight as set forth inclaim 3, wherein, in the separating step, the processed products areseparated by an air-blast separator into the high-specific-gravitysubstances composed substantially of a metal portion and into thelow-specific-gravity substances.
 11. The method of recycling acounterweight as set forth in claim 3, wherein, in the separating step,the processed products are magnetically separated by a conventionalmagnetic separator, and the processed products separated to amagnetic-substance side are further separated by an air-blast separatorinto the high-specific-gravity substances composed substantially of ametal portion and into the low-specific-gravity substances.
 12. Themethod of recycling a counterweight as set forth in claim 10, wherein awind power of the air-blast separator is 12 to 20 m/s.
 13. The method ofrecycling a counterweight as set forth in claim 4, wherein, in thecrushing/cutting step, a filler containing the metal portion is roughlycrushed to remove a large-sized metal portion, and thereafter theremaining filler portion is further crushed to destroy a combined statebetween the metal portion and the other filler.
 14. The method ofrecycling a counterweight as set forth in claim 4, wherein, in theseparating step, the processed products are separated by a magneticseparator of high peripheral speed/high magnetic force into thehigh-specific-gravity substances composed substantially of a metalportion and into low-specific-gravity substances.
 15. The method ofrecycling a counterweight as set forth in claim 5, wherein, in theseparating step, the processed products are separated by a magneticseparator of high peripheral speed/high magnetic force into thehigh-specific-gravity substances composed substantially of a metalportion and into low-specific-gravity substances.
 16. The method ofrecycling a counterweight as set forth in claim 4, wherein, in theseparating step, the processed products are magnetically separated by aconventional magnetic separator, and the processed products separatedonto a magnetic-substance side are further separated by a magneticseparator of high peripheral speed/high magnetic force into thehigh-specific-gravity substances composed substantially of a metalportion and into the low-specific-gravity substances.
 17. The method ofrecycling a counterweight as set forth in claim 5, wherein, in theseparating step, the processed products are magnetically separated by aconventional magnetic separator, and the processed products separatedonto a magnetic-substance side are further separated by a magneticseparator of high peripheral speed/high magnetic force into thehigh-specific-gravity substances composed substantially of a metalportion and into the low-specific-gravity substances.
 18. The method ofrecycling a counterweight as set forth in claim 7, wherein a peripheralspeed of the magnetic separator of high peripheral speed/high magneticforce is 300 to 500 m/min.
 19. The method of recycling a counterweightas set forth in claim 7, wherein a magnetic flux density of the magneticseparator of high peripheral speed/high magnetic force is more than 4000gausses.
 20. The method of recycling a counterweight as set forth inclaim 8, wherein a magnetic flux density of the magnetic separator ofhigh peripheral speed/high magnetic force is more than 4000 gausses. 21.The method of recycling a counterweight as set forth in claim 4,wherein, in the separating step, the processed products are separated byan air-blast separator into the high-specific-gravity substancescomposed substantially of a metal portion and into thelow-specific-gravity substances.
 22. The method of recycling acounterweight as set forth in claim 5, wherein, in the separating step,the processed products are separated by an air-blast separator into thehigh-specific-gravity substances composed substantially of a metalportion and into the low-specific-gravity substances.
 23. The method ofrecycling a counterweight as set forth in claim 4, wherein, in theseparating step, the processed products are magnetically separated by aconventional magnetic separator, and the processed products separated toa magnetic-substance side are further separated by an air-blastseparator into the high-specific-gravity substances composedsubstantially of a metal portion and into the low-specific-gravitysubstances.
 24. The method of recycling a counterweight as set forth inclaim 5, wherein, in the separating step, the processed products aremagnetically separated by a conventional magnetic separator, and theprocessed products separated to a magnetic-substance side are furtherseparated by an air-blast separator into the high-specific-gravitysubstances composed substantially of a metal portion and into thelow-specific-gravity substances.
 25. The method of recycling acounterweight as set forth in claim 11, wherein a wind power of theair-blast separator is 12 to 20 m/s.